Device for the continuous process for the production of controlled architecture materials

ABSTRACT

The device of the present invention delivers reactants to a reaction zone in a plug flow reactor. The feedblock encircles the reaction zone. Reactants enter the feedblock through an inlet port leading to a manifold for the delivery of reactants into a plurality of feed ports that are in connection with the reaction zone of a plug flow reactor. The invention additionally encompasses plug flow reactors including one or more feedblocks and the method of utilizing the feedblock for the reduction of radial variation in concentration upon entry of a reactant into the reaction zone.

BACKGROUND OF THE INVENTION

The present invention relates to a device and method that can be used toenhance circumferential or radial dispersion of reactants, minimizediversity in products and reduce reactor fouling by minimizing theradial variation in concentration in a plug flow reactor.

Plug flow reactors can be used for a wide range of reactions. Reactionscan be based on chemical or physical reactions to form compounds,polymers, small molecule materials, blends, alloys, biologically activespecies, or biological species. Chemical reactions include both organicand inorganic reactions. Blends and alloys can also be made in a plugflow reactor for example by physically mixing components. The blends oralloys may comprise, for example, polymers mixed with inorganics such assilica, carbon black, or clay forming nanocomposite type materials orother reinforced materials.

Plug flow reactors may be used with various polymer synthesismethodologies including any step-growth polymerization mechanisms, forexample, polycondensations; or chain-growth polymerization mechanisms,for example, anionic, cationic, free-radical, living free radical,coordination, group transfer, metallocene, ring-opening, and the like.(See Odian, “Principles of Polymerization” 3rd Ed., Wiley-Interscience,1991, NY, N.Y.). The synthesis of homopolymers; random copolymers; blockcopolymers; star-branched homo-, random, and block copolymers; andend-functionalized polymers is possible by using appropriatepolymerization techniques.

Various types of polymers can be prepared from different monomericmaterials, the particular type formed being generally dependent upon theprocedures followed in contacting the materials during polymerization.For example, random copolymers can be prepared by the simultaneousreaction of the copolymerizable monomers. Block copolymers are formed bysequentially polymerizing different monomers. The ability to formdifferent types of polymers through control of the polymerization isreferred to generally as controlled architecture. Controlledarchitecture polymers are designed with various types or variations ofmorphology including: linear, branched, star, combination network;variations in composition including: block copolymer, random copolymer,homopolymer, graft copolymer, tapered or gradient copolymer, and/orvariations in functionality including: end, site specific, telechelic,multifunctional, and macromonomers.

Variation in local concentrations of reactants within plug flow reactorsystems leads to greater diversity in the products. For example, theproducts of any given polymerization reaction are a mixture of polymermolecules of different molecular weights related to the length andcomposition of the individual chains. Living anionic polymerizationreactions are very fast and exothermic. Therefore the polymer chainswill tend to grow longer in localities within a plug flow reactor wherethe concentration of reactant monomer is relatively higher. Theresulting disparity in lengths of the different polymer chains increasesthe polydispersity index (PDI), a reflection of poor uniformity betweenindividual polymer chains produced by the reaction.

Block copolymers as an example of controlled architecture, are known toself assemble into 3-dimensional morphologies, which are tunable byvariations and constituent block sizes and overall molecular weights. Inorder to achieve a uniform morphology, all of the polymer chains shouldhave a uniform length in composition. This uniformity is reflected inthe polydispersity index (PDI). The uniformity also relates and controlsthe order/disorder transition (crystalline/amorphous properties) of theblock copolymer system. Compositional gradients also adversely affectblock copolymer properties. For example, in the synthesis of a blockcopolymer with a 50/50 mole % composition, there could be a statisticalmixture of compositions around that desired point which average to50:50, although composed of a broader distribution, for example 45:55,46:54, or 60:40 etc. In products with controlled architecture, varianceis preferably minimized.

A plug flow reactor equipped with a single point delivery system can beplagued by reactor fouling, due to concentration gradients in 3D space.This increases downtime and increases the need to clean the reactor,thus decreasing production rates and productivity. Fouling can occur dueto solubility differences associated with high and low molecular weightsystems. This effect can be especially prevalent in the synthesis ofamphiphilic block copolymers or polymer containing highly polarsegments. These materials tend to micellize and exhibit interesting orchallenging solubilities and adhesion to materials (i.e. the glassreactor and metal paddles). Examples of amphiphilic blocks are high acidcontent polymers which show decreased solubility in non-aqueous solventsand vinyl pyridine-containing block copolymers where high vinyl pyridinecontent block copolymers display limited solubility in typicalpolymerization solvents such as cyclohexane and toluene.

SUMMARY OF THE INVENTION

The device of the present invention delivers reactants to a reactionzone in a plug flow reactor. The device is a feedblock that encirclesthe reaction zone. Reactants enter the feedblock through an inlet portleading to a manifold inside the feedblock for the delivery of thereactants to a plurality of feed ports that are in connection with thereaction zone of the plug flow reactor. The feed ports are disposed tosurround the reaction zone in an equidistant manner for delivery of thereactants with minimized variation in radial reactant concentration. Theinvention additionally encompasses plug flow reactors including one ormore feedblocks and the method of utilizing the feedblock for thereduction of radial variation in concentration upon entry of a reactantinto the reaction zone. The PDI of polymers made with plug flow reactorscan be lowered with use of the device and method of the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example feedblock device of thepresent invention.

FIG. 2 is a cross-sectional view of the feedblock taken along line 2—2in FIG. 1.

FIG. 3 is a perspective view of an alternative embodiment of thefeedblock.

FIG. 4 is a perspective view of the first flange as seen from theoutside of the feedblock.

FIG. 5 is an alternative perspective view showing the inside withrespect to feedblock of the first flange.

FIG. 6 is a perspective view of the portside of main body.

FIG. 7 is an alternative perspective view of main body as seen from themanifold side.

FIG. 8 is a perspective view of the inside of second flange.

FIG. 9 is an alternative perspective view of second flange viewed fromthe outside of the feedblock.

DETAILED DESCRIPTION

The methods of the present invention improve the uniformity of reactantdelivery into a plug flow reactor, thereby minimizing the diversity inthe resulting products. The device of the present invention includes afeedblock for uniform delivery of reactants or other materials into thereaction zone of a plug flow reactor. The feedblock converts one or moresingle point inlet ports on the outside of the reactor into a pluralityof feed ports arranged in an equidistant manner around a circumferenceof the reaction zone inside the reactor. Use of the feedblock inreactions carried out in plug flow reactors reduces concentrationvariations, product compositional variability, reactor fouling, andimproves radial mixing.

Product diversity in the production of controlled architecture materialsis not desired. Preferably, the product, for example a polymer, willhave uniform molecular weight and uniform morphology. Molecular weightof a polymer is frequently expressed by both a number average and aweight average molecular weight. The ratio of the weight averagemolecular weight to the number average molecular weight is a measure ofthe polydispersity of a polymer sample. Therefore, in polymericmaterials, reduction of the PDI demonstrates improved monodispersity oruniformity of the product.

The feedblock is used to introduce fluid reactants or materials in awide variety of reactions carried out in plug flow reactors. Reactantsinclude, but are not limited to: monomers, solvent, slurries,macromonomers, quenching agents, coupling agents, deprotection agents,catalysts, and initiators. Reaction is defined broadly to include a widevariety of chemical and physical reactions. For example, the feedblockmay be applied to the production of polymeric materials, small-moleculeorganic materials, inorganics (such as nanoparticles or modifiedsilica), blended materials comprising at least one polymeric component,biological materials, and biologically active materials in plug flowreactors. Additional information regarding the application of plug flowreactors in a variety of reactions can be found in U.S. PatentApplication Publication No. US 2003/0035756 A1, owned by common assigneeand herein incorporated by reference.

The feedblock also addresses process issues related to reactor fouling.For example, materials such as amphiphilic block copolymers or polymerscontaining highly polar segments tend to micellize and exhibitinteresting and challenging solubilities and adhesion to the plug flowreactor itself. The tendency to micellize or adhere to portions of thereactor is facilitated when local environments of unusually high monomerconcentrations occur such as single port entry introduction of monomer.In cases where monomer has micellized or adhered to portions of thereactor typically a very few polymer chains having a very high molecularweight are produced. These chains are less soluble in the solvent andeventually may plug the reactor. These problems are prevented with useof the feedblock as local variation in concentration is reduced oreliminated because of uniform introduction of reactants and radialmixing of the reactants into the reaction zone. The polymer chainsresulting from plug flow reactors utilizing the feedblock have chains ofnearly all the same length and so are less likely to display reducedsolubility and fouling problem's.

An embodiment of feedblock 20 consistent with the present invention isshown in FIG. 1. Feedblock 20 is a body 22 defining a central opening24. Body 22 is not necessarily limited to the circular or disc-likeshape presented in FIG. 1, and alternatively may be modified to haveother external profiles. Feedblock 20 has a first end 26 with recess 28for connection to other portions of a plug flow reactor (not shown).Feedblock 20 similarly has a second end (not shown) with a recess (notshown) opposite of the first end 26. Central opening 24 has acylindrical shape with a circular circumference corresponding generallyto the reaction zone of a plug flow reactor. Central opening 24 offeedblock 20 may also be referred to as reaction zone 24. Reactants orother fluid materials are delivered into the feedblock 20 at inlet port30. The reactants subsequently exit body 22 and flow into reaction zone24 through a plurality of feed ports 32. The feed ports 32 are arrangedcircumferentially about reaction zone 24 in a uniform manner.

The operation of the reactant delivery system of feedblock 20 isportrayed in FIG. 2 as a cross-sectional view taken along line 2-2 ofFIG. 1. Feedblock 20 is designed to introduce reactants or othermaterials into the reaction zone of the plug flow reactor whileminimizing the radial variation in concentration. Reactants or otherfluid materials are delivered into feedblock 20 through an inlet port30. Inlet port 30 is in fluid connection with an annular-shaped manifold34 inside of feedblock.20. Manifold 34 is concentrically oriented aroundreaction zone 24. The fluid materials delivered through inlet port 30arc either pumped or otherwise pressurized so as to fill manifold 34.Manifold 34 is in fluid connection with a plurality of feed ports 32.Each feed port 32 is a narrow channel extending radially from manifold34 to the reaction zone. The fluid materials flow from manifold 34 intosubstantially all feed ports 32, which are in fluid connection withreaction zone 24 resulting in reactants entering reaction zone 24 at anarray of equidistant points placed to circumferentially surround thereaction zone. This uniform delivery of reactants reduces radialvariation in concentration in the reaction zone 24 at the point ofdelivery. By feeding the monomer into the reaction zone through manyholes around the circumference of the circular reaction zone rather thanthrough a single hole, local environments within the reactor where theconcentration of monomer is high are substantially eliminated.Additionally, radial mixing of the reactant into the reaction zone isfacilitated.

Feedblock 20 may alternatively be formed in multiple sections tofacilitate machining in construction of the inner structure. Analternative embodiment of feedblock 20 shown in FIG. 3 is formed ofthree sections: a first flange 38, a main body 36, and second flange 40.The structures comprising the reactant delivery system described in thepreceding paragraph are primarily formed in the main body 36. Main body36 is sandwiched between first flange 38 and second flange 40, whichserve to close the exposed openings of the reactant delivery system inmain body 36. Fastening means, including but are not limited to: bolts,clamps or any combination thereof, are used to secure first flange 38,main body 36 and second flange 40 into a single unit, feedblock 20.

Typically holes 42 are located in feedblock 20, including first flange38, main body 36 and second flange 40, to accommodate the fasteningmeans. Additional fastening means and holes 44 are employed to attachfeedblock 20 to portions of the plug flow reactor (not shown). Thenumber of holes and method of fastening may vary. The sections arepresented in further detail in FIGS. 4-9.

First flange 38 is shown in FIG. 4. First flange 38 includes first end26 with recess 28 and outer edge 46. Reaction zone 24 passes throughfirst flange 38. Recess 28 surrounds reaction zone 24 for coupling ofthe first flange 38 to the plug flow reactor (not shown). Recess 28 mayfor example receive a Teflon disc or o-ring(not shown), the disc havinga central opening, to assist in sealing the connection of the reactor tofirst flange 38 and therefore feedblock 20. First flange 38 as shown inFIG. 4 is rotated 180° to give the perspective of in FIG. 5, which showsbacking 48. Backing 48 is a predominately planar surface for contactwith main body 36.

Main body 36, shown in FIG. 6, comprises two parallel faces, portside 50and manifold side 52 (shown in FIG. 7 described below). Main body 36also includes outer edge 54, inner surface 56, feed port 32, and groove62. Main body 36 can generally be described as a ring-like structurebounded by outer edge 54 with inner surface 56 defining reaction zone24. Portside 50 and manifold side 52 (not shown) are predominantlyplanar opposing faces of main body 36. Portside 50 includes a pluralityof feed ports 32 and a groove 62. Groove 62 receives an 0-ring forsealing portside 50 against backing 48 of first flange 38. When portside50 of main body 36 is compressed against backing 48, an O-ring placed ingroove 62 seals against backing 48, which substantially closes theexposed channels of feed ports 32 creating a series of narrow radialpassageways that connect from manifold 64 (shown in FIG. 7) intoreaction zone 58.

Each feed port 32 is a channel in portside 50 such that the channelopens into inner surface 56 of main body 36. The feed ports 32 areformed in portside 50 such that the feed ports 32 are radially orientedrelative to inner surface 56 and reaction zone 24. The feed ports 32 arealso arranged in portside 50 such that they are equidistant from eachother and are therefore uniformly distributed circumferentially aroundreaction zone 24.

A plurality of feed ports 32 is desired in portside 50. The minimumnumber of feed ports 32 is approximately 4 with the maximum number offeedports 32 being limited only by available space, machiningrequirements and the desired reactant flow. Approximately, twelve feedports 32 are preferred with about 64 feed ports 32 being most preferred.Smaller plug flow reactors prefer smaller numbers of feed ports 32,while larger volume plug flow reactors prefer larger numbers of feedports 32.

The perspective of main body 36 is reversed in FIG. 7 so that manifoldside 52 is visible. Manifold side 52 includes manifold 64, inner groove66, outer groove 68 and inlet port 30. Manifold 64 is an annular recessin the substantially planar manifold side 52. Openings into feed ports32 are visible inside manifold 64. Inlet port 30 extends from outer edge54 into manifold 64. Main body 36 may alternatively include a pluralityof inlet ports 30 with access to manifold 64 when high flow rates areneeded. Inner groove 66 and outer groove 68 each receive an O-ring suchthat when manifold side 52 of main body 36 is pressed against backing 70(described below) of second flange 40, manifold 64 is completed tocreate an annular space.

Second flange 40 is shown in FIG. 8. Second flange 40 has a ring-likeshape defined by outer edge 72, inner surface 74, backing 70, and secondend 76 (not shown). Second flange 40, as shown in FIG. 8, has increasedthickness to accommodate additional optional inlet ports 78 which passfrom, outer edge 72 through second flange 40 into inner surface 74 foraccess to the reaction zone 24. These inlet ports 78 have variouspurposes including: to withdraw samples; access for a thermal couple orother monitoring equipment; a plurality of holes, typically threeuniformly distributed holes, for shaft alignment pins to support amixing shaft (not shown); and single point inlet ports for introductionof reactants or solvents, or removal of products or reaction samples. InFIG. 8, second flange 40 has several single point inlet ports includinga sample withdrawal port 80, three holes 82 (two of which are visible inouter edge 72 and the third which is visible on inner surface 74) forshaft alignment pins (not shown), and at least one access port 78 thatmay be used for thermal couple or other access to reaction zone 24.Backing 70 of second flange 40 is primarily planar so as to seal againstthe manifold side 52 of main body 36.

Second end 76 of second flange 40 is shown in further detail in thereversed perspective of FIG. 9. Second end 76 includes recess 84 andholes 42 and holes 44. Recess 84 assists attachment of second flange 40to the plug flow reactor (not shown). Typically an O-ring of Teflon orother material used to assist in sealing will be placed in recess 84 forcontact with other portions of the plug flow reactor (not shown).

As noted above, second flange 40 has increased thickness to accommodateadditional ports for access to the reaction zone. These ports areoptional and may not be necessary in all plug flow reactors includingfeedblock 20. Where these ports, including: inlet port 78, samplewithdrawal port 80, shaft pin holes 82, are eliminated; second flange 40may have decreased thickness. Alternatively, first flange 38 may beincreased in thickness to accommodate additional ports as described insecond flange 40.

Plug Flow Reactor

The feedblock and method of the present invention is generallycompatible with any plug flow reactor. The plug flow reactor may be anyapparatus that allows materials to pass through it in a plug flowmanner, for example, a stirred tube reactor, an extruder, a staticmixer, or any combination in series. “Plug flow reactor (PFR)” means areactor that ideally operates without axial mixing (see An Introductionto Chemical Engineering Kinetics and Reactor Design; Charles G. Hill J.Wiley and Sons 1977, p. 251). A plug flow reactor is able to impel, fromthe input end of reactor to its output end, in an essentially plug flowmanner, the reaction mixture contained therein. “Essentially plug flow”means that eddies and dead spots, where reaction mixture can be delayedin its path through reactor and short circuits to the reactor outlet,which allow the reaction mixture to pass too quickly through reactor,are virtually nonexistent. This means that a “plug” (a theoretical sliceof a reaction mixture cut in a direction perpendicular to the overalldirection of flow in a reactor) continues down the length of plug flowreactor with about the same velocity profile as a plug traveling throughthe reactor either earlier or later in time. The manner in which areaction mixture is impelled through plug flow reactor can be by anexternal means such as a pressure feed, for example a pump, or by aninternal means, for example a screw in an extruder. Plug flow can beassisted by lateral mixing means, for example, radial paddles in astirred tubular reactor (STR).

One example of a plug flow reactor is a stirred tubular reactor (STR),which consists of a series of cylinders joined together to form a tube.The ability to add reagents at numerous points along the reaction,pathway in a STR makes the STR well suited for controlled architecturereactions. Down the center of this tube, the STR typically has a shafthaving a plurality of paddles radiating therefrom. An external driverotates the shaft causing the paddles to stir the reaction mixture andassist in heat transfer. In addition, the paddles are commonly designedsuch that they assist the pumps and/or pressure feed systems inpropelling the reaction mixture through the STR.

STRs are described as examples of plug flow reactors, and are meant tobe merely illustrative. Objects, and advantages of this invention arefurther illustrated by the following examples. The particular materialsand amounts thereof, as well as other conditions and details, recited inthese examples should not be used to unduly limit this invention.

EXAMPLES

The use of the feedblock and method of reactant delivery in a plug flowreactor is demonstrated in the following examples. The feedblock isincorporated in a STR used for living anionic polymerizations of blockco-polymers. “Living anionic polymerization” means, in general, a chainpolymerization reaction that proceeds via an anionic mechanism withoutchain termination or chain transfer. (For a more complete discussion ofthis topic, see Anionic Polymerization Principles and Applications. H.L. Hsieh, R. P. Quirk, Marcel Dekker, New York, N.Y. 1996. Pg 72-127).

In a living polymerization, each polymer chain has a reactive site,called a “living end”, for further addition of monomer. Livingpolymerization reactions can be used to form different morphologiesincluding portions of a polymer chain in which all the neighboringmonomer units (except at the transition point) are of the same identity,also called a “block”. For example, AAAAAABBBBBB is a diblock copolymercomprised of A and B monomer units. For further information regardingthe use of plug flow reactors for anionic polymerizations, includingliving anionic polymerizations, and formation of various controlledarchitectures, see U.S. Pat. No. 6,448,353 owned by common assignee andherein incorporated by reference.

Continuous temperature controlled anionic polymerization processes forthe synthesis of controlled architecture materials, such as thosedescribed in U.S. Pat. No. 6,448,353, typically produce polymers withpolydispersities of 1.5-2.5. In these systems, monomers and catalyst arcadded at a single location in 3-dimensional (D) space, thus creating alocal environment where there is an unusually high content of monomerresulting in a concentration gradient in 3D space. This broadens thepolydispersity of the overall 3D slice of material in a plug flowreactor because some chains grow at faster rates than others due toconcentration differences. The feedblock and method of the presentinvention improves (lowers) the polydispersity of these reactions byreducing concentration gradients.

Test Methods

Molecular Weight and Polydispersity

The average molecular weight and polydispersity of a sample wasdetermined by Gel Permeation Chromatography (GPC) analysis.Approximately 25 mg of a sample was dissolved in 10 milliliters (mL) oftetrahydrofuran (THF) to form a mixture. The mixture was filtered usinga 0.2 micron polytetrafluoroethylene (PTFE) syringe filter. Then about150 microliters (μL) of the filtered solution was injected into aPlgel-Mixed B column (available from Polymer Laboratories, Amherst,Mass.) that was part of a GPC system also having a Waters® 717Autosampler and a Waters® 590 Pump (available from Waters Corporation,Milford, Mass.). The system operated at room temperature, with a THFeluent that moved at a flow rate of approximately 0.95 mL/min. An ErmaERC-7525A Refractive Index Detector (available from JM Science Inc.Grand Island, N.Y.) was used to detect changes in concentration. Numberaverage molecular weight (M_(n)) and polydispersity index (PDI)calculations were based on a calibration mode that used narrowpolydispersity polystyrene controls ranging in molecular weight from6×10⁶ to 600×10₆. The actual calculations were made with PL Caliberssoftware available from Polymer Laboratories, Amherst, Mass.

Block Concentration

The concentration of different blocks in a block copolymer wasdetermined by Nuclear Magnetic Resonance (NMR) spectroscopy analysis. Asample was dissolved in deuterated chloroform to a concentration ofabout 10 weight % and placed in a Unity® 500 MHz NMR Spectrometeravailable from Varian Inc., Palo Alto, Calif. Block concentrations werecalculated from relative areas of characteristic block componentspectra.

TABLE 1 Materials Used Material Description Isoprene Available fromAldrich Chemical Co., Milwaukee, WI. Styrene Available from AshlandChemical, Columbus, OH. t-Butyl methacrylate Available from Sans EstersCorp., New York, NY. Diphenylethylene Available from Acros/FisherScientific, Itasca, IL. Sec-Butyl lithium Available from AldrichChemical Co., Milwaukee, WI 1.3 Molar in cyclohexane. Toluene Availablefrom Worum Chemical, St. Paul, MN Tetrahydrofuran (THF) Available fromISP Technologies, Wayne, NY. Cyclohexane Available from AshlandChemical, Columbus, OH.

Monomer Preparation and Handling

The reactant monomers in the examples (isoprene, styrene, t-butylmethacrylate, and diphenylethylene were nitrogen sparged until the O₂concentration was less than 1 part per million (ppm). Deoxygenatedmonomer was pumped through a column (1=50 cm, d=2 cm) of basic alumina(Al₂O₃, activated, acidic, Brockmann I, about 150 mesh, Sigma-AldrichFine Chemicals, Milwaukee, Wis.). The purified monomer was then feddirectly to the first zone of a stirred tubular reactor (STR) when usedfor the initial block, or at a later zone of the STR for a subsequentblock formation. Reaction solvents (either toluene, cyclohexane or amixture) were pumped through molecular sieve beads (available as Zeolite3A from UOP LLC, Des Plaines, Ill.) and fed directly to the STR. Inisoprene-based examples where a THF co-solvent was used, the THF alsowas deoxygenated by nitrogen sparging for 30 minutes and purified bypumping through both 3A molecular sieve beads (available as Zeolite 3A,UOP LLC, Des Plaines, Ill.) and a column of alumina (available as Al₂O₃,activated, acidic, Brockmann I, about 150 mesh, Sigma-Aldrich FineChemicals, Milwaukee, Wis.). The THF stream was then fed to the STR inthe same zone as the isoprene or one zone after the isoprene feed point.Sec-butyl lithium initiator(1.3 Molar (M) sec-butyl lithium incyclohexane) was diluted by addition of pre-purified cyclohexane and wasadded to the first zone of the STR.

Pumps were used to deliver the monomers, solvents, and initiators to thereactor. Typical pumps for this application are reciprocating pistonpumps, models QG50 and QG150 from Fluid Metering Inc. Syosset, N.Y.Pressure feeding the materials from pressurized vessels is anotherviable method, but requires more sophisticated backpressure regulationor badger valves to achieve accurate flowrates, such as a Brooks®Quantim® low flow coriolis mass flow controllers (Brooks Instrument,Hatfield Pa.).

STR Descriptions 3.3 L Glass STR

One example stirred tubular reactor (STR) had a reaction zone capacityof 3.33 L and consisted of five jacketed (shell-and-tube) glass sections(Pyrex® cylinders). The tube had an inner diameter of 4.13 cm and anouter diameter of 5.08 in. The shell had a diameter of 8.89 cm. The STRhad five sections, the first and third zones were 60.96 cm long, thesections for the second and fourth zones were 30.48 cm long, and thesection for the fifth zone was 68.58 cm long. The sections were joinedtogether with stainless steel connector disks. A feedblock consistentwith the present invention Was placed as a connector disk between thefourth and fifth zone. The feedblock had 12 feed ports in the mainbodyfor the introduction of monomers into the reaction zone of the reactorthrough 12 points around the circumference, in a circular fashion. Thefeedblock additionally had a single point inlet port in the secondflange for purposes of comparison of products. The STR was closed off atboth ends with stainless steel disks.

The connector disks were equipped with individual temperature sensingdevices extending into the interior of the cylindrical sections. Thesetemperature-sensing devices permitted the temperature of the reactionmixture in each section to be monitored and adjusted up or down (asnecessary) to, a set point by varying the temperature of the heattransfer fluid flowing through the jacketed sections.

Extending through the center of the joined cylinders was a 0.95 cmdiameter stainless steel shaft suspended along the cylinder axis byshaft alignment pins. To the shaft were affixed 60 detachable stainlesssteel paddles with approximately 2.1 cm between each paddle. Therectangular paddles were 3.2 mm thick, 1.91 cm wide, and 3.81 cm long.The paddle configuration used was as follows; in zone 1, 14 rectangularpaddles; in zone 2, seven rectangular paddles; in zone 3, 14 rectangularpaddles; in zone 4, seven rectangular paddles; and in zone 5, 18rectangular paddles. The shaft was attached to a 2.2 kW variable speedmotor and driven at approximately 150 rpm .

0.94 L Glass STR

A second example STR had a reaction zone capacity of 0.94 L andconsisted of five jacketed (shell-and-tube) glass sections (Pyrex®cylinders). The tube had an inner diameter of 3.01 cm and an outerdiameter of 3.81 cm. The shell had a diameter of 6.4 cm. All fivesections, corresponding to zones 1-5, were 25.4 cm long. The sectionswere joined together by stainless steel coupling disks. The couplingdisks were equipped with individual temperature sensing thermocouplesextending into the interior of the cylindrical sections. Thesethermocouples permitted the temperature of the reaction mixture in eachsection to be monitored and adjusted up or down (as necessary) to a setpoint by varying the temperature of the heat transfer fluid flowingthrough the jacketed sections. The coupling disks also contained varioussingle inlet ports through which monomer or solvent could be added intothe reaction mixture. The coupling disk located between the fourth andfifth zones was designed in such a way that the monomer would enter thedisk, fill a circumferential chamber inside the disk, and then enter thereactor through 12 points equally spaced around the center of thereactor. The disk positioned at the beginning of the first zone wasdesigned in a similar fashion with the ability to feed monomer into thereactor through 12 equally spaced holes around the circumference of thereactor.

Extending through the center of the joined cylinders was a stainlesssteel shaft with a length 132.9 cm and a diameter of 0.95 cm. The shaftwas suspended along the cylinder axis by shaft alignment pins. Thirtydetachable stainless steel paddles with approximately 2.1 cm betweeneach paddle were affixed to the shaft. The rectangular paddles were 1.6mm thick, 1.91 cm wide, and 2.32 cm long. Each zone contained sixpaddles. The shaft was attached to a variable speed, ¼ hp Baldor®industrial gear motor (Baldor® Industrial Motor, Ft. Smith, Ark.) with atorque of 3.6 Nm. The stir rate was controlled at approximately 150 rpm.An external seal, typically a Chesterton® 440 seal (A.W. Chesterton,Colo., Stoneham, Mass.) is used to seal the front end of the reactor.

Heat transfer was accomplished by attaching recirculators to thejackets. All zones were heated or cooled with water. They were allindependently heated or cooled except zones 2 and 3, which wereheated/cooled in series from the same recirculator. Zone 1 washeated/cooled in a co-current manner while the other four zones wereheated/cooled in a countercurrent fashion. Typical heat transfer fluidsinclude but are not limited to oil, water, or HFE 7100 (available from3M Corporation, St. Paul, Minn.) and are chosen based on the desiredtemperature range needed. A typical heating/cooling bath for mostanionic polymerizations is the Julabo™ FP50 (Julabo USA, Inc.,Allentown, Pa.). It is ideal to have one unit dedicated to each section,but at times it is possible to have multiple sections connected inseries to the same heat transfer unit.

Temperatures in the reactor can be monitored and recorded through use ofa thermocouple temperature recorder (OCTTEMP 8-channel recorder, OmegaEngineering, Inc. Stamford, Conn.) and accompanying software interfacedwith a personal computer. Thermocouples (type J) are positioned in eachof the stainless steel coupling pieces to provide zone batchtemperatures during polymerizations.

Example 1 Poly(styrene-t-butyl methacrylate) Block Copolymer—3.3 L STR

This example illustrates the effect of introducing a monomer into thereactor at twelve points equally spaced around the circumference has onthe polydispersity index. A comparison will be made whereby all thereactor and reaction conditions are constant from sample to sampleexcept for the method of introducing the monomer into the reactor.

An initiator slurry was prepared by mixing 320 g of 1.3 M sec-butyllithium in cyclohexane with 4000 g of oxygen-free cyclohexane andstirred at room temperature for about 30 minutes. Purified styrenemonomer and purified cyclohexane solvent were fed into the first zone ofthe STR via reciprocating piston pump. The initiator slurry wasintroduced by peristaltic pump into zone 1 of the STR as well. A colorchange from clear to red was observed in zone 1 when the initiatorsolution contacted the monomer, and an exotherm resulted. The reactiontemperature was kept at about 53° C. by adjusting the jacket temperatureof zone 1 to 58° C. The temperature of the reaction mixture in each ofthe 5 zones of the STR was individually maintained at: #1=53° C., #2=42°C., #3=28° C., #4=28° C., and #5=20° C.

The materials flowed through the first three zones, facilitated bystirring paddles along the reaction path. Polymerization continued toessentially 100% completion by the end of zone 3, thereby forming a“living” polystyrene polymer mixture. At the start of, zone 4, purifieddiphenylethylene (DPE) was fed via reciprocating piston pump to the“living” polystyrene reactive mixture, resulting in a slight colorchange, from red to a deeper red, indicating that a reaction hadoccurred with the DPE and the “living” polystyrene polymer. At thebeginning of zone 5, purified t-butyl methacrylate (tBMA) was fed viareciprocating piston pump to the “living” polymer solution, resulting ina color change from deep red to white indicative of “living” polytBMApolymer. The tBMA feed was alternated between 12 points around thecircumference using a feedblock consistent with the present inventionand 1 point using a single inlet port to produce sample product for eachcombination of feed method and set of flowrates. The resultingpoly(styrene-tBMA) block copolymer was quenched with deoxygenatedmethanol and samples were collected for analysis. The flowrates of allthe raw materials were varied during the run and are listed in Table 2.The total residence time for these reactions was about 20 minutes.

Each sample was tested for number average molecular weight (Mn),polydispersity index (PDI) and relative concentration of polystyrene tot-butyl methacrylate. Results are shown in Table 3.

TABLE 2 Analytical Results for PS-tBMA Block Copolymers tBMA Cyclo- MnMw Entry hexane BuLi Styrene DPE TBMA PS tBMA g/mol × g/mol × Samplepoints g/min g/min g/min g/min g/min mol % mol % 10⁴ 10⁴ PDI 1A 12 80.010.0 25 9.2 10.1 76.6 23.4 5.72 8.11 1.42 1B 1 80.0 10.0 25 9.2 10.167.3 32.7 5.01 7.52 1.50 2A 12 80.0 10.0 25 9.2 12.1 66.8 33.2 6.22 8.251.33 2B 1 80.0 10.0 25 9.2 12.1 70.3 29.7 4.76 7.20 1.51 3A 12 80.0 10.025 9.2 16.1 65.3 34.7 7.34 9.74 1.33 3B 1 80.0 10.0 25 9.2 16.1 66.333.7 7.45 10.42 1.40 4A 12 80.0 10.0 25 9.2 18.1 65.1 34.9 7.11 9.841.38 4B 1 80.0 10.0 25 9.2 18.1 60.4 39.6 6.83 10.77 1.58 5A 12 80.010.0 25 9.2 20.1 64.8 35.2 6.45 9.44 1.46 5B 1 80.0 10.0 25 9.2 20.162.3 37.7 6.61 10.11 1.53 6A 12 80.0 10.0 34 9.2 20.1 66.5 33.4 8.7212.15 1.39 6B 1 80.0 10.0 34 9.2 20.1 68.2 31.7 8.82 12.85 1.46

Example 2 Poly(styrene-isoprene) Block Copolymer—0.9 L STR

This example illustrates the effect of introducing a monomer into thereactor at twelve points equally spaced around the circumference has onthe polydispersity index. In this example the monomer for the firstblock is fed into the reactor through 12 points around the circumferenceof the STR. This demonstrates a typical polydispersity attained withthis device.

In this example, all materials were fed from pressure vessels maintainedat 50 psi by nitrogen. The feed rates were all controlled with Brooks®Quantim® low flow coriolis mass flow controllers, available from BrooksInstrument, Hatsfield, Pa. An initiator slurry was prepared by mixing100 g of 1.3 M sec-butyl lithium in cyclohexane with 3000 g ofoxygen-free cyclohexane and stirred at room temperature for about 30minutes. Purified styrene monomer (5.9 g/min), purified toluene solvent(9.6 g/min), and the initiator slurry (5.5 g/min) were fed into the STRat the beginning of the first zone. The styrene was fed into the reactorthrough 12 points equally spaced around the circumference of the tube. Acolor change from clear to red was observed in zone 1 when the initiatorsolution contacted the monomer. The reaction temperature in the firstzone was kept at about 50° C. by adjusting the jacket temperature ofzone 1 to 60° C.

The materials flowed through the first two zones, facilitated bystirring paddles along the reaction path. Polymerization continued toessentially 100% completion by the end of zone 2, thereby forming a“living” polystyrene solution. Purified isoprene monomer was fed intothe reactor (5.9 g/min) at the beginning of zone 3. A color change fromred to clear resulted. Purified THF was fed into the reactor (0.7 g/min)at the beginning of Zone 4. A color change from clear to yellow resultedand an exotherm was observed. The jacket temperatures were maintainedat: #1=60° C., #2=46° C., #3=46° C., #4=60° C., #5=60° C. The resultingpoly(styrene-isoprene) block copolymer was quenched with deoxygenatedmethanol and samples were-collected for analysis. The . flowrates of allthe raw materials were held constant throughout the run (6 hours). Thetotal residence time for this reaction was about 32 minutes and the,reaction was carried-out at 43% solids.

Each sample was tested for number average molecular weight (Mn),polydispersity index (PDI) and relative concentrations of polystyrene topolyisoprene. Results are shown in Table 3.

TABLE 3 Analytical Results for PS-PI Block Copolymers Mn Mw g/mol ×g/mol × PS 1,2 PI 1,4 PI 3,4 PI Sample 10⁴ 10⁴ PDI mol % mol % mol % mol% 2A 3.98 4.87 1.22 41.3 0.0 51.9 6.8 2B 4.10 4.87 1.19 40.4 0.6 50.38.7 2C 3.98 4.76 1.20 41.4 0.7 48.7 9.2 2D 3.95 4.75 1.20 42.3 0.6 47.69.5 2E 3.83 4.79 1.25 42.3 1.0 42.3 14.3 2F 3.95 4.81 1.22 42.1 1.9 34.521.5 2G 3.81 4.72 1.24 42.2 1.5 38.4 17.9 2H 4.06 4.92 1.21 40.7 2.333.0 23.9

Example 3 Poly(styrene-t-butyl methacrylate) Block Copolymer—0.9 L STR

This example illustrates the effect introducing a monomer into thereactor at twelve points equally spaced around the circumference has onreactor fouling and on the polydispersity index. In this example,poly(styrene-t-butyl methacrylate) block copolymer was produced byfeeding the monomer for the first block of the polymer(styrene) into thereactor using a feedblock with 12 feed ports and by feeding the monomerfor this second block (t-butyl methacrylate) through a second feedblockwith 12 feed ports between zones 4 and 5. This product is produced for 3hours, and then the feed of the second monomer was changed to a singlepoint inlet port to produce a comparison (control) product for anadditional 3 hours.

In this example, all materials were fed from pressure vessels maintainedat 50 psi by nitrogen. The feed rates were all controlled with Brooks®Quantim® low flow coriolis mass flow controllers, available from BrooksInstrument, Hatsfield, Pa. Initiator slurry was prepared by mixing 63 gof 1.4 M sec-butyl lithium in cyclohexane with 3000 g of oxygen-freecyclohexane and stirred at room temperature for about 30 minutes.Purified styrene monomer (6.1 g/min), purified cyclohexane solvent (12.3g/min), and the initiator slurry (5.5 g/min) were fed into the STR atthe beginning of the first zone. The styrene was fed into the reactorthrough 12 points equally spaced around the circumference of the tube. Acolor change from clear to red was observed in zone 1 when the initiatorsolution contacted the monomer. The reaction temperature in the firstzone was kept at about 60° C. by adjusting the jacket temperature ofzone 1 to 60° C. The temperature of the reaction mixture in each of the5 zones of the STR was individually maintained at: #1=60° C., #2=45° C.,#3=36° C., #4=34° C., and #5=38° C.

The materials flowed through the first three zones, facilitated bystirring paddles along the reaction path. Polymerization continued toessentially 100% completion by the end of zone 3, thereby forming a“living” polystyrene polymer mixture. At the start of zone 4, purifieddiphenylethylene (DPE) was fed via reciprocating piston pump to the“living” polystyrene reactive mixture, resulting in a slight colorchange, from red to a deeper red, indicating that a reaction hadoccurred with the DPE and the “living” polystyrene polymer. The DPE isintroduced to modify the “living” polymer chain ends to induce moreefficient methacrylate initiation to prevent reduce side reactions suchas chain transfer, backbiting, and termination.

At the beginning of zone 5, purified t-butyl methacrylate (tBMA) was fedvia reciprocating piston pump to the “living” polymer solution,resulting in a color change from deep red to white indicative of“living” polytBMA. The tBMA was fed into the reactor through 12 feedports of the feedblock for 3 hours thereby producing product by themethod of the present invention. The method of monomer deliver wasswitched to a single inlet for another 3 hours and an additional productwas collected. The resulting poly(styrene-tBMA) block copolymer wasquenched with deoxygenated methanol and samples were collected foranalysis. The total residence time for these reactions was about 25minutes.

Each sample was tested for number average molecular weight (Mn),polydispersity index (PDI) and relative concentration of polystyrene tot-butyl methacrylate. Representative results are shown in Table 4.

TABLE 4 Analytical Results for PS-tBMA Block Copolymers TBMA Entry Mng/mol × Mw g/mol × PS TBMA Sample Points 10⁴ 10⁴ PDI mol % mol % 3A 125.03 9.44 1.88 67.8 32.2 3B 1 5.59 19.3 3.44 66.7 33.3

While the PS-tBMA block copolymer was being synthesized, pressures inthe reactor were recorded as a means of quantifying reactor fouling. Asthe reactor fouls, polymer precipitates out of solution and adheres tothe reactor wall and the stirring paddles. This causes a polymerobstruction that in turn creates an overall pressure increase in thereactor. During the synthesis using the tBMA feed through, 12 feedports, no pressure increase and no polymer build-up was observed. Whilefeeding the tBMA into the reactor through 1 point, the same polymerrapidly became insoluble and began to foul the reactor. With thissetting, a pressure of 7 psi was observed.

The samples collected from feeding tBMA into the reactor through onepoint displayed bimodal behavior in the GPC analysis. Further analysisof a polymer sample was done to determine the makeup of this highermolecular weight peak. A GPC sample was fractionated and the differentfractions were analyzed via NMR. The results show that there is not auniform distribution of tBMA to all polymer chains in the polymerproduced by single inlet monomer feed. Some of the polymer chains hadmuch more tBMA than the average and as such became insoluble. Theresults are shown in Table 5.

TABLE 5 NMR Analysis for PS-tBMA Block Copolymer Fractions Sample PS mol% TBMA mol % 3B (Overall Sample) 66.7 33.3 4A (Main Peak) 71.8 28.2 4B(Higher MW “shoulder”) 44.6 55.4

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be unduly limited to the illustrativeembodiments set forth herein.

1. A device for providing a reactant to a reaction zone in a plug flowreactor, the device comprising: a feedblock configured to substantiallyencircle the reaction zone; an inlet port providing entry of thereactant into the feedblock; a manifold disposed within the feedblockand in fluid connection with the inlet port; and a plurality of reactantfeed ports disposed in the feedblock for delivering reactant to thereaction zone and fluidly connected with the manifold such that thereactant is delivered to the reactant feed ports.
 2. The device of claim1 wherein the plurality of uniformly distributed feed ports are disposedaround the reaction zone in a substantially equidistant manner.
 3. Thedevice of claim 2 wherein the manifold is an annular chamber extendingcircumferentially through the main body.
 4. The device of claim 1 havingat least 4 feed ports.
 5. The device of claim 1 having at least 12 feedports.
 6. The device of claim 1 wherein the feedblock includes a firstflange portion, a mainbody, and a second flange portion wherein thecentral portion provides fluid contact of the feed ports with thereaction zone and the first and second flange sections provide for fluidconnection with the plug flow reactor.
 7. A plug flow reactorcomprising: a plug flow reactor chamber; a reactant feedblock in fluidconnection with the plug flow reactor chamber wherein the feedblockincludes a plurality of substantially uniformly spaced circumferentiallydistributed reactant feed ports disposed to provide a reactant to thereactor chamber and a manifold disposed within the feedblock and fluidlyconnected with the feed ports for distributing reactant to the feedports.
 8. The plug flow reactor of claim 7 wherein the reactantfeedblock includes an inlet feed port fluidly connected to the manifold.9. The plug flow reactor of claim 7 including a plurality ofspaced-apart feedblocks disposed along the reactor chamber, wherein thereactant feed ports of each feedblock are disposed for providingreactant into the reactor chamber.
 10. The plug flow reactor of claim 7including a plurality of feedblocks disposed in an adjacent manner alongthe reactor chamber wherein the feed ports of each feedblock aredisposed to provide reactant into the reactor chamber.